Linear voice coil motors in tape drive systems are known. For example, the 9840 tape drive system from Storage Technology uses magneto-restrictive (MR) elements in its read/write head and a voice coil linear actuator to position the head with respect to the tape. This type of tape head does not tolerate a large external magnetic field as it operates to sense magnetic fields on the surface of the tape. Specifically, it is desirable to keep the magnetic field in the vicinity of the read/write head below five Orsted.
One problem with the prior art voice coil linear actuator is it produces a relatively large fringing field (approximately forty Orsted) at the bottom of the head, even with magnetic shielding. Consequently, prior art voice coil linear actuator systems effectively permit only a short stroke to traverse a linear track of about 0.015 inch. While this is fine for tape drive systems that record in one tape band, with the head spread over the entire tape width; this short stroke is not sufficient for recording in two bands to span a distance of nearly 0.300 inch. Furthermore, systems that record in two tape bands require a much larger linear actuator in order to provide performance in linear torque over the entire distance. By contrast, the short stroke prior art actuators translate almost entirely within the actuator.
One object of the invention is thus to provide a long stroke voice coil linear actuator. Another object of the invention is to provide a voice coil linear actuator for the 9840 Eagle Drive system by Storage Technology, with reduced magnetic fringing from the actuator.
These and other objects will become apparent in the description that follows.